Wednesday, May 7, 2014

A Dog Without A Head - K9 Assembly Testing

So this is another quick blog entry. Last night I did a test assembly of the main body, the dorsal control panel and the drive base. I just wanted to see how (and if) the parts fit together. This video features the new right side door which I will talk about more below.

For the longest time, I never bothered to manufacture a right, side door. This is where the classic K9 logo will go when the body is finished but up until now it was just a big access hole. The door needed to be custom fitted because even though it is draw out in the BBC plans, the body itself has a unique shape because it is built out of wood and glue as opposed to metal which would be far more rigid. I started with a cardboard test cut out which I roughly cut to fit and made adjustments on that. Then I duplicated this in particle board and spent quite a while sanding the edges until it just fit the hole.

It is interesting to point out that the lower portion of this door is angled down about 6 degrees to conform with the way the body itself is angled. Rather than cut and join two pieces of wood, I routed a horizontal line through the particle board along where the angle change occurs just thick enough to make the wood bendable. I then bent it into shape and filled the routed channel with plastic wood.

This turned out to work really well. The resulting door was a perfect fit and once it was sanded and sealed, looked like a natural bend in a single piece of metal.

This door will be held in place with four magnetic cabinet door catches so it will be secure but come off easily. You are also looking at the primed finish, not the final finish which I am waiting to apply until the entire body is complete. I will probably go with the dark blue metallic finish of the K9 Mk III as shown here when done.

Tuesday, May 6, 2014

Raspberry Hal

I wanted to keep a Raspberry PI running at my desk at work full time here at PTC but I wanted to have it out of the way. It would be available if I needed a system that remained at work while I was away with my laptop. I also wanted it as a test platform for some work I have just started doing on the ThingWorxs  platform and the "Internet of Things". Now you know me, I like to build electronics into science fiction replicas so I thought, why not build a Raspberry PI case into the polyurethane Hal replica I have hanging on my cube wall. Here is a shot of him from the day I put an Apple sticker on him before any modifications.

Unfortunately, he was made almost entirely out of solid, cast polyurethane. I tried to hollow him out with a Dremel tool but it was going to take a long time and be very messy because of the excessive dust it was generating. Because of this, I decided to recreate a hollow version of him in wood. I already had some experience creating control panels out of wood for my K9 project so I knew I could do a pretty convincing job. I had already installed a battery to light his eye and a light sensor on the polyurethane prop to turn the eye light off when the office was dark to conserve on battery power. I could reuse these in the new Hal.

For those of you who don't know much about Hal, he was the shipboard computer on the spacecraft Discovery One that tried to murder his entire crew when he felt they would interfere with his carrying out his mission in the movie 2001, A Space Odyssey. Here is a clip of him in action.

I wanted my new Hal to hold a Raspberry PI, some environmental sensors, an amplifier and his own speakers, all powered off of a single cell phone wall charger. He would be capable of playing appropriate Hal clips from the movie as well as responding to simple spoken commands. He should also serve as a Thingworx test platform for reporting metrics based off of the sensors I planed to install.

Here is a sentimental moment with Hal on my workbench saying his first words.

It was kind of creepy to hear him speak for the first time.

Here is the completed project now hanging on my cube wall. The prop has now been entirely rebuilt out of wood. He is fastened to the wall cloth with two pins that come out of the back of the unit at a 45 degree angle like a picture frame nail. This allows him to be easily removed for service.

One thing I did not expect was that when he is mounted flush to the wall, his temperature rises until he goes into thermal shutdown. It turns out that the PI generates so much heat that adequate ventilation is required. If there is no way for this heat to escape, the inside of the case can reach temperatures in excess of 50 degrees Celsius (122 degrees fahrenheit)! I had to bring him home and install four small legs that make him stand 1/4" back from the wall to allow for proper convection cooling. Now he stays at a cool 44 degrees C (111 degrees F).

Here is a shot of the back and side of the case with callouts for the parts inside. The only sensor I have installed so far was the original light sensor I took from the original polyurethane model I started with. I am adding a sound card (for speech recognition), external temperature sensor and an infra-red proximity sensor next. I will also replace the wire wrapping (the thin red wire nest) with a real cable.

I am planning on publishing the details of how to re-produce this project on Instructables soon along with the software running on the PI.